JP4720337B2 - Image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a printer, a copying machine, a facsimile, or a multifunction machine having these functions, which employs an electrophotographic method, and particularly detects the film thickness of an image carrier such as a photosensitive drum. It is about technology.

Japanese Patent Publication No. 2-21591 Japanese Patent No. 3005138

  In recent years, image forming apparatuses such as printers, copiers, facsimiles, or multifunction machines having these functions that employ this type of electrophotographic method have been associated with the increase in frequency of use in offices. In order to eliminate the time required for maintenance of the apparatus as much as possible and realize maintenance-free by the user, it is desired to extend the life.

  In the above-described image forming apparatus, as a technique for extending the life of a member to be charged such as a photosensitive drum charged by a charging unit such as a charging roll, there is a technique for controlling the discharge charge amount by the charging unit such as a charging roll to be constant. . This technique for controlling the discharge charge amount to be constant detects the discharge charge amount between the charging means and the member to be charged, and the discharge charge amount discharged from the charging member toward the member to be charged is a predetermined value. In this way, by controlling the applied voltage and the current value to be energized, the occurrence of image defects due to defective charging is not affected by the film thickness, temperature, humidity and other environmental conditions of the body to be charged or the contamination of the charging means. In other words, the life of the charged body such as the photosensitive drum is extended by minimizing the stress on the charged body.

  By the way, the surface of the photosensitive member such as the photosensitive drum is worn with use, and the film thickness of the photosensitive layer gradually decreases. When used in a state where the film thickness of the member to be charged is reduced beyond a certain value, charging failure or image defect occurs.

  Therefore, in order to prevent charging failure and image defects from occurring due to the decrease in the film thickness of the charged body, as disclosed in JP-A-5-223513, etc., the current flowing through the charged body If the film thickness of the object to be charged is decreased beyond a certain value, the charged object may be replaced, and charging defects and image defects may occur. Techniques to prevent this have been proposed.

  A thickness detection device for a charged body according to Japanese Patent Laid-Open No. 5-223513 includes an electrode member that contacts the charged body, a voltage applied to the electrode member, and a current (direct current) flowing through the electrode member. However, more specifically, the electrode member that contacts the member to be charged, the voltage applied to the electrode member, and the electrode member thereby Means for detecting the thickness of the member to be charged based on the current flowing through the power source, and a current detecting unit having a frequency filter circuit in a closed circuit composed of a power source for applying a voltage to the electrode member, the electrode member, and the member to be charged. It is configured.

  However, the conventional technique has the following problems. That is, in the case of the technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 5-223513, a device for measuring a DC voltage must be provided separately inside the image forming apparatus, and the number of parts of the image forming apparatus is reduced. In addition to the increase in cost, the sequence becomes complicated.

  In the case of the technique disclosed in the above Japanese Patent Laid-Open No. 5-223513, in order to detect the film thickness of the charged object from the direct current, it is necessary to rotate the charged object at least once or more except during image formation. There is also a problem that the member to be charged is worn by that amount, and the life of the member to be charged is shortened.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to measure a direct current in order to detect the film thickness of the member to be charged. It is not necessary to provide a new device, effectively utilizing the means provided in the image forming apparatus that controls the discharge charge amount to a constant level, without increasing the number of parts and increasing the cost, and unnecessarily being charged. An object of the present invention is to provide an image forming apparatus capable of detecting the film thickness of the charged body without rotating the body.

That is, according to the first aspect of the present invention, a charging roll configured by covering a surface of a metal core with a conductive layer is brought into contact with the surface of the photosensitive drum, and an AC voltage is superimposed on the metal core of the charging roll. An apparatus for forming an image by charging the surface of the photosensitive drum by applying a direct current voltage, a charge amount detecting means for detecting a discharge charge amount between the charging roll and the photosensitive drum; and In an image forming apparatus including a control unit that controls a discharge amount between a charging roll and a photosensitive drum to be constant, and an environment detection unit that detects an environmental condition.
The charging roll and the photosensitive member detected by the charge amount detecting unit in a state in which the regular discharging charge amount between the charging roll and the photosensitive drum is controlled to be a predetermined value by the control unit . Thickness calculation for calculating the thickness of the photosensitive layer of the photosensitive drum based on the amount of discharge charge opposite to the specified value and the detection information of the environment detection means out of the discharge charge amount with the drum An image forming apparatus comprising the means.

  The invention described in claim 2 is the image forming apparatus according to claim 1, further comprising a film thickness display means for displaying the film thickness calculated by the film thickness calculation means.

  According to the present invention, there is no need to newly provide a means for measuring a direct current in order to detect the film thickness of the member to be charged, and the image forming apparatus for controlling the discharge charge amount to be constant is provided. An image forming apparatus capable of detecting the film thickness of the object to be charged without effectively increasing the number of parts and increasing the cost without unnecessarily rotating the object to be charged. Can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1
FIG. 1 is a block diagram showing a full-color multifunction peripheral as an image forming apparatus according to Embodiment 1 of the present invention. This color multifunction machine also has a function as a copying machine, a printer, or a facsimile. Of course, the image forming apparatus may individually constitute a copying machine, a printer, a facsimile, or the like.

  As shown in FIG. 2, the color multifunction peripheral 1 includes a scanner 2 as an image reading device at the top thereof, and is connected to a personal computer (not shown) via a network (not shown).

  The color multifunction device functions as a fax machine that copies an image of a document read by a scanner, prints based on image data sent from a personal computer, and transmits / receives image data via a telephone line. It is like that.

  In FIG. 2, reference numeral 1 denotes a main body of a color multifunction peripheral. An automatic document feeder (ADF) that automatically conveys unshown originals one by one is provided on the upper portion of the color multifunction peripheral main body 1. ) 2 and an image input device (IIT) 3 for reading an image of a document conveyed by the automatic document conveying device 2. The image input device 3 illuminates a document placed on the platen glass 4 with a light source 5, and reduces a reflected light image from the document including a full-rate mirror 6, half-rate mirrors 7 and 8, and an imaging lens 9. Scanning exposure is performed on an image reading element 10 composed of a CCD or the like via the optical system 11, and the color material reflected light image of the original is read by the image reading element 10 at a predetermined dot density (for example, 16 dots / mm). It has become.

  The reflected light image of the original read by the image input device 3 is, for example, the image processing device 12 (IPS) as reflectance data of three colors of red (R), green (G), and blue (B) (each 8 bits). In this image processing apparatus 12, shading correction, position shift correction, lightness / color space conversion, gamma correction, frame erasing, color / moving editing, etc. are performed on the original image data as necessary. In addition, the predetermined image processing is performed as described later. The image processing apparatus 12 also performs predetermined image processing on image data sent from a personal computer (not shown) or the like.

  The image data that has been subjected to the predetermined image processing by the image processing device 12 is similarly processed by the image processing device 12 as yellow (Y), magenta (M), cyan (C), black (K) (each 8 bits). ), And as described below, yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13Y, 13M, 13C, and 13K. Are sent to a common ROS (Raster Output Scanner) 14, and the ROS 14 as the image exposure apparatus performs image exposure with laser light LB in accordance with gradation data of a predetermined color. Of course, not only a color image but also a monochrome image may be formed.

  By the way, as shown in FIG. 2, an image forming unit A is disposed inside the color MFP main body 1. The image forming unit A includes yellow (Y), magenta (M), and cyan. Four image forming units 13Y, 13M, 13C, 13K of (C) and black (K) are arranged in parallel at a constant interval in the horizontal direction.

  These four image forming units 13Y, 13M, 13C, and 13K are all configured in the same manner, and roughly divided, a photosensitive drum 15 as an image carrier that is rotationally driven at a predetermined speed, and the photosensitive drum. A charging roll 16 for primary charging that uniformly charges the surface of 15, and an ROS 14 as an image exposure device that forms an electrostatic latent image by exposing an image corresponding to a predetermined color on the surface of the photosensitive drum 15. And a developing unit 17 for developing the electrostatic latent image formed on the photosensitive drum 15 with toner of a predetermined color, and a cleaning device 18 for cleaning the surface of the photosensitive drum 15. These photosensitive drums 15 and image forming members disposed in the periphery are integrally unitized, and are configured to be individually replaceable from the color multifunction peripheral body 1.

  As shown in FIG. 2, the ROS 14 is configured in common to the four image forming units 13Y, 13M, 13C, and 13K, and modulates four semiconductor lasers (not shown) in accordance with the gradation data of each color, Laser light beams LB-Y, LB-M, LB-C, and LB-K are emitted from these semiconductor lasers according to gradation data. Of course, the ROS 14 may be individually configured for each of a plurality of image forming units. The laser beams LB-Y, LB-M, LB-C, and LB-K emitted from the semiconductor laser are irradiated to the polygon mirror 19 through an f-θ lens (not shown), and are deflected and scanned by the polygon mirror 19. The The laser beams LB-Y, LB-M, LB-C, and LB-K deflected and scanned by the polygon mirror 19 are exposed to exposure points on the photosensitive drum 15 through an imaging lens (not shown) and a plurality of mirrors. Then, scanning exposure is performed obliquely from below.

  As shown in FIG. 2, the ROS 14 scans and exposes an image on the photosensitive drum 15 from below. Therefore, the ROS 14 includes four image forming units 13Y, 13M, 13C, and 13K located above. There is a possibility that toner or the like may fall from the developing unit 17 and be contaminated. Therefore, the periphery of the ROS 14 is hermetically sealed by a rectangular parallelepiped frame 20, and four laser beams LB-Y, LB-M, LB-C, and LB-K are placed on the upper portion of the frame 20, Transparent glass windows 21Y, 21M, 21C, and 21K as shield members are provided for exposure on the photosensitive drums 15 of the image forming units 13Y, 13M, 13C, and 13K.

  From the image data processing device 12, the ROS 14 is provided in common for the image forming units 13Y, 13M, 13C, and 13K for each color of yellow (Y), magenta (M), cyan (C), and black (K). The image data of each color is sequentially output, and the laser beams LB-Y, LB-M, LB-C, and LB-K emitted according to the image data from the ROS 14 scan the surface of the corresponding photosensitive drum 15. Exposure is performed to form an electrostatic latent image. The electrostatic latent images formed on the photosensitive drum 15 are respectively developed in yellow (Y), magenta (M), cyan (C), and black (K) colors by developing units 17Y, 17M, 17C, and 17K. Developed as a toner image.

The yellow (Y), magenta (M), cyan (C), and black (K) toner images sequentially formed on the photosensitive drums 15 of the image forming units 13Y, 13M, 13C, and 13K are as follows. Multiple transfer is performed by four primary transfer rolls 26Y, 26M, 26C, and 26K on an intermediate transfer belt 25 as an endless belt member of the transfer unit 22 disposed over the image forming units 13Y, 13M, 13C, and 13K. Is done. These primary transfer rolls 26Y, 26M, 26C, and 26K are disposed on the back side of the intermediate transfer belt 25 corresponding to the photosensitive drums 15 of the image forming units 13Y, 13M, 13C, and 13K. The primary transfer rolls 26Y, 26M, 26C, and 26K in this embodiment use volume resistance values that have been adjusted to a resistance of 10 ⁵ to 10 ⁸ Ωcm. The primary transfer rolls 26Y, 26M, 26C, and 26K are connected to a transfer bias power source (not shown), and a transfer bias having a polarity opposite to a predetermined toner polarity (positive polarity in the present embodiment) is predetermined. It is applied at the timing.

  Further, as shown in FIG. 2, the intermediate transfer belt 25 is wound around the drive roll 27, the tension roll 24, and the backup roll 28 with a certain tension, and has excellent constant speed (not shown). The drive roll 27 is rotationally driven by a dedicated drive motor and is circulated at a predetermined speed in the direction of the arrow. The intermediate transfer belt 25 is made of, for example, a belt material (rubber or resin) that does not cause charge-up.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred in multiple onto the intermediate transfer belt 25 are pressed against the backup roll 28 as shown in FIG. The secondary transfer roll 29 is secondarily transferred onto the sheet 30 as a sheet material, and the sheet 30 on which the toner images of these colors are transferred is conveyed to a fixing device 40 positioned above. The secondary transfer roll 29 is in pressure contact with the side of the backup roll 28, and secondary-transfers each color toner image onto a sheet 30 conveyed from below to above.

  The paper 30 is a sheet of a predetermined size from any of the paper feed trays 31, 32, 33, 34 arranged in a plurality of stages at the lower part of the color MFP main body 1, and is fed by a feed roll 35, a retard roll 36, etc. In a state where they are separated one by one, the paper is fed through a paper conveyance path 38 provided with a conveyance roll 37. Then, the paper 30 fed from any of the paper feed trays 31, 32, 33, 34 is temporarily stopped by the registration roll 39, and synchronized with the image on the intermediate transfer belt 25 by the registration roll 29. The sheet is fed again to the secondary transfer position of the intermediate transfer belt 25.

  As shown in FIG. 2, the sheet 30 on which the toner images of the respective colors are transferred is subjected to a fixing process with heat and pressure by a fixing device 40, and then the image forming surface is faced down by a conveying roll 41. An upper portion of the apparatus main body 1 is discharged by a discharge roll 44 provided at an outlet of the first paper transport path 43 through a first paper transport path 43 for discharging to a face down tray 42 as a single discharge tray. It is discharged onto a face-down tray 42 provided in.

  Further, when the paper 30 on which the image is formed as described above is discharged with the image forming surface facing upward, as shown in FIG. 2, face up as the second discharge tray with the image forming surface facing upward is performed. A discharge roller 47 provided at the outlet of the second paper transport path 46 through the second paper transport path 46 for discharging to the tray 45 causes a side portion (left side surface in the figure) of the apparatus main body 1. The paper is discharged onto a face-up tray 45 provided in

  In the above-described color multifunction peripheral, when full-color double-sided copying is performed, the sheet 30 with the image fixed on one side is directly discharged onto the face-down tray 42 by the discharge roll 44 as shown in FIG. Instead, the conveyance direction is switched by a switching gate (not shown), the discharge roll 44 is temporarily stopped and then reversely rotated, and the discharge roll 44 conveys the sheet to the double-sided sheet conveyance path 48. Then, the sheet 30 is conveyed again to the registration roll 39 in the state where the front and back of the sheet 30 are reversed by the conveyance roller 49 provided along the conveyance path 48. Then, after the image is transferred and fixed on the back surface of the paper 30, it is discharged to either the face-down tray 42 or the face-up tray 45 through the first paper transport path 43 or the second paper transport path 46. The

  In FIG. 2, 50Y, 50M, 50C, and 50K are toner cartridges that supply toner of a predetermined color to the developing device 17 of each color of yellow (Y), magenta (M), cyan (C), and black (K). , 51 denotes a cleaning device that removes transfer residual toner and the like on the intermediate transfer belt 25, respectively.

  FIG. 3 shows each image forming unit of the color multifunction peripheral.

  The four image forming units 13Y, 13M, 13C, and 13K for yellow, magenta, cyan, and black are all configured in the same manner as shown in FIG. 3, and these four image forming units 13Y, 13Y, In 13M, 13C, and 13K, as described above, yellow, magenta, cyan, and black toner images are sequentially formed at a predetermined timing. As described above, the image forming units 13Y, 13M, 13C, and 13K for the respective colors are each provided with the photosensitive drum 15, and the surface of the photosensitive drum 15 is uniformly provided by the charging roll 16 for primary charging. Charged. Thereafter, the surface of the photosensitive drum 15 is scanned and exposed to an image forming laser beam LB emitted from the ROS 14 according to the image data, and an electrostatic latent image corresponding to each color is formed. The laser beam LB that is scanned and exposed on the photosensitive drum 15 is set so as to be exposed from an obliquely lower side slightly to the right of the photosensitive drum 15. The electrostatic latent image formed on the photosensitive drum 15 is converted into yellow, magenta, cyan, and black colors by the developing rolls 17a of the developing units 17 of the image forming units 13Y, 13M, 13C, and 13K. The visible toner images are developed with toner, and these visible toner images are sequentially transferred in multiple onto the intermediate transfer belt 25 by the charging of the primary transfer roll 26.

  Residual toner, paper dust, and the like are removed from the surface of the photosensitive drum 15 after the toner image transfer process by the cleaning device 18 to prepare for the next image forming process. The cleaning device 18 includes a cleaning blade 18a, and the cleaning blade 18a removes residual toner, paper dust, and the like on the photosensitive drum 15.

  By the way, this embodiment is an apparatus for forming an image by charging the surface of a member to be charged by a charging unit, and a charge amount detecting unit for detecting a discharge charge amount between the charging unit and the member to be charged. An image forming apparatus comprising: a control unit that controls a discharge amount discharged from the charging unit toward the member to be charged; and an environment detection unit that detects an environmental condition. Based on the result, it is configured to include a film thickness calculating means for calculating the film thickness of the object to be charged together with the environmental condition detected by the environment detecting means.

  In this embodiment, the film thickness display means for displaying the film thickness calculated by the film thickness calculation means is provided.

  That is, as shown in FIG. 1, the color multifunction peripheral according to this embodiment includes yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13Y, 13M, 13C, 13K is provided with charging rolls 16 as charging means for uniformly charging the surface of the photosensitive drum 15 to a predetermined potential. The charging roll 16 is configured by covering the surface of a metal core 60 made of metal such as stainless steel with a conductive layer 61 made of conductive synthetic resin or synthetic rubber whose resistance value is adjusted to a predetermined value. The release layer is coated on the surface of the conductive layer 61 as necessary. The charging roll 16 generates a minute gap discharge in a minute gap between the charging roll 16 and the surface of the photosensitive drum 15 by applying an alternating voltage on which a direct current voltage is superimposed by a high voltage power source 62 to the metal core 60. The surface of the photosensitive drum 15 is charged by the discharge.

  The voltage applied to the charging roll 16 is set such that the DC voltage is approximately DC 700 to 800 V, which is substantially equal to the charging potential of the photosensitive drum 15, the AC voltage is 1.5 to 2.0 kV, and the frequency is approximately 1300 Hz. As a result, an AC current as shown in FIG. 4 flows through the charging roll 16 basically except for the DC component.

  The control circuit 63 that also functions as a charge amount detection unit, which is a control unit of the above-described color multifunction peripheral, makes the discharge charge amount between the charging roll 16 and the photosensitive drum 15 constant at a predetermined value. In addition, the high voltage power supply 62 is controlled. Therefore, the control circuit 63 detects the alternating current Iac flowing through the charging roll 16 via the high-voltage power supply 62, and determines the amount of discharge charge between the charging roll 16 and the photosensitive drum 15 based on the alternating current Iac. It comes to calculate.

  That is, the control circuit 63 detects the alternating current Iac flowing through the charging roll 16 via the high-voltage power supply 62, calculates the half-wave area per unit time of the alternating current, and the charging roll 16 and the photoconductor. A discharge charge amount between the drum 15 and the drum 15 is calculated.

  Thereafter, the control circuit 63 applies the high voltage power supply 62 so that the discharge charge amount between the charging roll 16 and the photosensitive drum 15 is constant at a predetermined value (for example, 55 μC / sec). It is comprised so that AC voltage etc. may be controlled. At this time, the discharge charge amount opposite to the specified value is not constant, but varies depending on the environment and film thickness.

  Then, the control circuit 63 determines the discharge charge amount and the photosensitive drum film thickness as shown in FIG. 5 based on the discharge charge amount opposite to the specified value between the charging roll 16 and the photosensitive drum 15. The film thickness of the photosensitive drum 15 is calculated based on a graph or a table showing the relationship between At this time, since the relationship between the discharge charge amount opposite to the specified value and the film thickness of the photosensitive drum has environment dependency depending on the environment such as temperature and / or humidity, the control circuit 63 It is configured to refer to detection information from an environment detection sensor 64 as an environment detection means including a temperature sensor and a humidity sensor.

  The relationship between the discharge charge amount opposite to the specified value and the film thickness of the photosensitive drum has a linear relationship if the temperature and humidity are constant. As the relationship changes, the dependent linear relationship also changes. For example, in a high temperature and high humidity environment where the temperature is 30 ° C. and the relative humidity is 70%, the relationship between the discharge charge amount opposite to the specified value and the film thickness of the photosensitive drum is linear, but the photosensitive drum It has a characteristic that the value of the discharge charge amount is opposite to the specified value for the film thickness. In contrast, in a low-temperature and low-humidity environment where the temperature is 10 ° C. and the relative humidity is 10%, the relationship between the discharge charge amount opposite to the specified value and the film thickness of the photosensitive drum is substantially the same as that at high temperature and high humidity. Although it has the same gradient, it has a characteristic that the value of the discharge charge amount is opposite to the specified value for the film thickness of the photosensitive drum. In a normal environment where the temperature is 20 ° C. and the relative humidity is 40%, the relationship between the discharge charge amount opposite to the specified value and the film thickness of the photosensitive drum is smaller than that at high temperature and high humidity. Thus, the value of the discharge charge opposite to the specified value for the film thickness of the photosensitive drum has a characteristic that is located between high temperature and high humidity and low temperature and low humidity.

  Note that the relationship between the discharge charge amount opposite to the specified value and the film thickness of the photosensitive drum does not need to be approximated by a single straight line over the entire area of the film thickness of the photosensitive drum. You may approximate by the several straight line and curve which have.

  Further, in the example of FIG. 6, only high temperature and high humidity, normal temperature and normal humidity, and low temperature and low humidity have been described. However, the environmental conditions are further subdivided, and each of the environmental conditions is opposite to the specified value. Needless to say, the relationship between the amount of discharge charge at the pole and the film thickness of the photosensitive drum may be obtained.

  In the above configuration, in the color multifunction peripheral according to this embodiment, it is not necessary to newly provide a means for measuring a direct current as described below, and the image forming apparatus controls the discharge charge amount to be constant. Can effectively detect the film thickness of the object to be charged without causing an increase in the number of parts and cost, and without unnecessarily rotating the object to be charged. It has become.

  That is, in the color multifunction peripheral according to the above embodiment, as shown in FIG. 2, each of the image forming units 13Y, 13M, 13C, yellow (Y), magenta (M), cyan (C), and black (K) At 13K, yellow (Y), magenta (M), cyan (C), and black (K) toner images are formed, and these yellow (Y), magenta (M), cyan (C), and black (K) ) Are transferred onto the intermediate transfer belt 25 in a multiple manner to form a full-color or monochrome image.

  At that time, in each of the yellow (Y), magenta (M), cyan (C), and black (K) image forming units 13Y, 13M, 13C, and 13K, as shown in FIG. However, the toner is charged to a predetermined potential by the charging roll 16, and a toner image of a predetermined color is formed. At this time, the surface of the photosensitive drum 15 is damaged by the electric discharge generated between the charging roll 16 and gradually wears during the image forming process, so that the photosensitive layer on the surface of the photosensitive drum 15 is used. The film thickness will gradually become thinner.

  In this embodiment, as shown in FIG. 1, when the surface of the photosensitive drum 15 is charged by the charging roll 16, the discharge charge amount between the photosensitive drum 15 and the charging roll 16 is a predetermined value. The discharge charge amount is controlled so as to be constant, and when the photosensitive drum 15 is charged by the charging roll 16, the discharge charge amount is calculated by the control circuit 63.

  Then, the control circuit 63 refers to a graph or table as shown in FIG. 6 based on the discharge charge amount opposite to the specified value at a predetermined timing, and the temperature and humidity by the environment detection sensor 64. The film thickness of the photosensitive drum 15 is calculated in consideration of this detection information. For example, when the control circuit 63 determines that the temperature and humidity detection information by the environment detection sensor 64 is a normal temperature and humidity environment in which the temperature is 20 ° C. and the relative humidity is 40%, the control circuit 63 has a polarity opposite to the specified value. When the discharge charge amount is −30 μC / sec, the film thickness of the photosensitive drum 15 is calculated to be about 32 μm.

  As shown in FIG. 1, the control circuit 63 displays the calculation result of the film thickness of the photosensitive drum 15 on a film thickness display device 65 provided on an operation panel or the like of the color multifunction peripheral. The control circuit 63 may always display the calculation result of the film thickness of the photosensitive drum 15 on the film thickness display device 65, but the film thickness of the photosensitive drum 15 needs to be exchanged. When it becomes thinner, for example, only when it becomes less than 15 μm, or when it becomes a value close to 15 μm, it is necessary to replace the value or the photosensitive drum 15, or a new image forming unit is ordered. A message indicating that it is necessary to do so may be displayed on the film thickness display device 65 provided on the operation panel of the color multifunction peripheral.

  As described above, in the color multifunction peripheral according to the above-described embodiment, it is necessary to provide means for detecting a direct current flowing in the charging roll or to rotate the photosensitive drum only for detecting the film thickness of the photosensitive drum. In addition, there is no need to newly provide a means for measuring direct current, and the means provided in the image forming apparatus for controlling the discharge charge amount to be used effectively can be used to increase the number of parts and increase the cost. It is possible to detect the film thickness of the object to be charged without incurring and unnecessarily rotating the object to be charged.

FIG. 1 is a block diagram showing a main part of a color multifunction peripheral as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a block diagram showing a color multifunction peripheral as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a block diagram showing the image forming unit of the color multifunction peripheral as the image forming apparatus according to Embodiment 1 of the present invention. FIG. 4 is a graph showing the amount of electric charge discharged between the photosensitive drum and the charging roll of the color multifunction peripheral as the image forming apparatus according to Embodiment 1 of the present invention. FIG. 5 is a graph showing the relationship between the film thickness of the photosensitive drum and the discharge charge amount.

Explanation of symbols

  15: photosensitive drum, 16: charging roll, 62: high-voltage power supply, 63: control circuit, 64: environmental sensor, 65: film thickness display device.

Claims (2)

A charging roll formed by coating the surface of the core metal with a conductive layer is brought into contact with the surface of the photosensitive drum, and a DC voltage in which an AC voltage is superimposed on the core metal of the charging roll is applied to the photosensitive drum . an apparatus for image forming by charging the surface, the charging roller and the charge amount detecting means for detecting a discharge charge quantity between the photosensitive drum, discharge charge between the charging roll and the photosensitive drum In an image forming apparatus comprising a control means for controlling the amount to be constant and an environment detection means for detecting environmental conditions,
The charging roll and the photosensitive member detected by the charge amount detecting unit in a state in which the regular discharging charge amount between the charging roll and the photosensitive drum is controlled to be a predetermined value by the control unit . Thickness calculation for calculating the thickness of the photosensitive layer of the photosensitive drum based on the amount of discharge charge opposite to the specified value and the detection information of the environment detection means out of the discharge charge amount with the drum An image forming apparatus comprising: means. The image forming apparatus according to claim 1, further comprising a film thickness display unit that displays the film thickness calculated by the film thickness calculation unit.

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